1. Field
The following description relates to a field effect transistor including phosphorus-doped graphene and a production method thereof, and phosphorus-doped graphene and a method of producing the same.
2. Description of Related Art
A graphene is a molecule having the structure of a 2-dimensional honeycomb lattice monolayer composed of carbon atoms. Graphene exhibits excellent properties such as high thermal conductivity (˜5000 Wm−1K−1), high mobility of electric charge carriers (200,000 cm2V−1 s−1), large specific surface area (2,630 m2 g−1) and high mechanical stability. Due to these excellent properties, since its first discovery in 2004, a great deal of attention has been paid by researchers to explore the possible application of graphene to various fields. By way of example, graphene application has been considered for a wide range of applications, including a field effect transistor (FET), a supercapacitor, a hydrogen generation/storage, a solar cell, a photocatalyst, a biosensor, to name a few.
Graphene is particularly attracting attention as an available candidate material for future electronics. As the Si-based electronics is expected to meet a problem of size limit, development of a new material capable of replacing Si is strongly desirable. Graphene has advantageous properties such as ballistic transport of charges on nano scale, and graphene can be deeply doped by gate voltage or molecular adsorption without suffering a great loss in carrier mobility. The superlative electric transfer characteristics of the graphene may be controlled by selecting a doping source with discretion and adjusting the amount of doping.
In this regard, Korean Patent No. 2010-0111999 discloses a field effect transistor using graphene as a channel layer.
Further, since it is first reported by K. S. Novoselov and A. K. Geim in a paper titled “Two-dimensional gas of massless Dirac fermions in graphene” (Nature, vol. 438, p. 197, 2005) that graphene has an electric transfer characteristic that is switchable between electron and hole channels by means of varying a gate voltage, many research groups have studied controlling the electrical characteristics of the graphene for the purpose of its application to electronics. Some researches considered using NO2, H2O and iodine as acceptors, whereas using NH3, CO and ethanol as donors. Graphene shows a P-type (hole conductor) electric transfer characteristic curve when it is doped with acceptor molecules. However, graphene also shows an N-type (electron conductor) electric transfer characteristic curve when it is doped with donor molecules. Since graphene may exhibit both the N-type conductivity and the P-type conductivity characteristics by being doped with atoms capable of giving or receiving electrons easily, the width of its research and the range of its application are deemed to be very wide. In general, a graphene semiconductor channel exhibits P-type conductivity characteristics in the oxygen atmosphere or in the air by being doped with oxygen. Besides, even an N-type graphene semiconductor channel tends to be easily converted to a P-type channel in exposure to the air by being doped with oxygen. However, in order to develop a complementary circuit graphene device in which a P-type transistor and an N-type transistor coexists, it is very important to develop an N-type graphene semiconductor channel in which the N-type conductivity characteristics can be stably maintain and maximized in exposure to the air.
Researches that used doping and a complex in order to maximize either the N-type conductivity characteristics or the P-type conductivity characteristics have been reported. Further, test results regarding the stability of a P-type graphene semiconductor device have also been reported. So far, however, a graphene semiconductor channel device that is stable when exposed to the air and is capable of maintaining a P-type characteristic for a long time has yet to be reported.
Further, there is a strong demand for developing a method capable of maintaining the N-type conductivity characteristics of a graphene stably in exposure to the air.